SEDIMENT CHARACTERISTICS INFLUENCING THE BIOAVAILABILITY OF NONPOLAR ORGANIC CONTAMINANTS TO DIPOREIA SPP

Organic carbon is considered the major variable affecting the bioavail ability of non-polar, sediment-associated contaminants. Previously, va riation in bioavailability for some Great Lakes sediments compared to a soil material was nearly a factor of 10 after carbon normalization. Because a soil might not truly represent sedimentary materials, sedime nts and soils were gathered from several locations in the United State s, Canada, and Finland. The accumulation kinetics of the amphipod Dipo reia spp, were measured for pyrene, benzo[a]pyrene (BaP), 2,4,2',4'-te trachlorobiphenyl (TCBP), and 2,4,5,2',4',5'-hexachlorobiphenyl (HCBP) sorbed to sediments and soils. The organic carbon content of the sedi ments ranged from 0.45-21.2% and 32.2-45.0% for soils. The bioavailabi lity, measured as the uptake clearance (amount of source compartment c leared of contaminant per mass of organism per hour), was controlled b y the amount of organic carbon, particularly for the chlorinated biphe nyls. However, for polycyclic aromatic hydrocarbons (PAH), bioavailabi lity was controlled more by the organic carbon polarity represented by the carbon/nitrogen ratio of the sediment. PAH bioavailability increa sed as the ratio increased; thus, the more nonpolar the organic matter , the more available the compound. This polarity did not account for a ny of the chlorinated biphenyl bioavailability. The amount and type of mineral matrix of the sediment did not influence the bioavailability for either compound class. In addition, the amount of oxygen in the se diment was correlated with the bioavailability for BaP after carbon no rmalization.